Operations performed on machines similar in principle to a lathe have been automated to the extent that a complete series of cuts can be performed without the operator's attention, after the machine has been properly prepared. The control systems have been based usually on perforated or magnetically recorded tapes, or by direct computer programming. A common example of such a machine in a modern shop is the chucking machine, in which bar stock or blanks are rotatively machined according to specifications. These machines are often referred to as "NC" (numerically controlled), or "CNC" (computer numerically controlled). Essentially, these machines consist of a heavy frame supporting a rotating spindle, and providing a guideway on which a carriage moves axially with respect to the spindle. The carriage sometimes has a transverse guideway engaging a cross-slide carrying the turret, which can be angularly indexed about its axis (usually vertical) to present different tools in sequence to the workpiece. The control system is responsible for determining all of these movements.
The control system "knows" the position of a reference surface on the turret, but does not initially "know" where the cutting point of each tool is with respect to such a reference. These tools can be for specialized lathe turning, or for drilling, boring, threading, or any other standard operation. In order for the automatic control system to function, the displacement of the cutting point from the reference must be determined, and this information must be inserted in the control system. The standard procedure to accomplish this is to "touch off" each tool against a reference piece held in the chuck, either visually, or by the use of a light controlled by contact of the tool with the surface of the reference piece. This is very time-consuming, and requires the attention of a very highly skilled operator. Determining this data on one widely used machine requires 50 to 55 steps for each tool carried by the turret. All of this represents shop time in which the expenses are on-going, an the machine is out of production. The present invention is directed at providing equipment and procedure that will simplify this work, and render it much more efficient.